Nucleating agents

ABSTRACT

A composition includes a thermoplastic polyester or polyolefin; and a nucleant having a chemical formula: 
     
       
         
         
             
             
         
       
     
     and combinations of any two or more thereof; where each R 1  is independently H, NR 2 R 2 , OH, OR 2 , SR 2 , SOR 2 , SO 2 R 2 , CN, COR 2 , CO 2 R 2 , CONR 2 R 2 , NO 2 , F, Cl, Br, or I; and each R 2  is independently H or C 1 -C 6  alkyl.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 11/022,954, filed Dec. 27, 2004, which in turn claims thebenefit of U.S. Provisional Patent Application Ser. No. 60/533,640,filed Dec. 30, 2003, the contents of which are incorporated herein byreference in their entireties for any and all purposes.

TECHNICAL FIELD

The invention relates to nucleants, thermoplastics compositions thatinclude such nucleants, and related methods and articles.

BACKGROUND

Thermoplastics can be used to fabricate a wide array of products. Whenpreparing semicrystalline thermoplastics for processing, it is oftendesirable to add a nucleant to the semicrystalline thermoplastic tomanipulate the rate at which the thermoplastic crystallizes. Bymanipulating the crystallization rate, the rate at which thethermoplastic loses tackiness, as well as the mechanical strength of thefinished thermoplastic, can be controlled.

SUMMARY

The invention relates to nucleants, thermoplastics compositions thatinclude such nucleants, and related methods and articles.

In one aspect, the invention features a composition that includes athermoplastic polyester or polyolefin and a nucleant. The nucleant caninclude a compound that includes a nitrogen-containing heteroaromaticcore.

Embodiments can include one or more of the following features.

The nitrogen-containing heteroaromatic core can be pyridine, pyrimidine,pyrazine, pyridazine, triazine, or imidazole.

The compound can have a chemical formula of Formula 1, Formula 2,Formula 3, Formula 4, Formula 5, or Formula 6 (all of which aredescribed in detail below) and combinations thereof, wherein each R1 isindependently H, NR²R², OH, OR², SR², SOR², SO₂R², CN, COR², CO₂R²,CONR²R², NO₂, F, Cl, Br, or I; and each R² is independently H or C₁-C₆alkyl.

The composition can include a thermoplastic polyester.

The thermoplastic polyester can include an aliphatic polyester.

The aliphatic polyester can be selected from the group consisting ofpolybutylene succinates, polycaprolactones, polyhydroxyalkanoates,polyglycolic acids, polylactic acids, and combinations thereof.

The aliphatic polyester can include a polyhydroxyalkanoate.

The polyhydroxyalkanoate can be a polyhydroxyalkanoate homopolymerselected from the group consisting of poly-3-hydroxybutyrate, polylacticacid, polyglycolic acid, and poly-4-hydroxybutyrate.

The polyhydroxyalkanoate can be a copolymer of 3-hydroxybutyrate and atleast one co-monomer selected from the group consisting of3-hydroxypropionate, 3-hydroxyvalerate, 3-hydroxyhexanoate,3-hydroxyheptanoate, 3-hydroxyoctanoate, 3-hydroxynonaoate,3-hydroxydecanoate, 3-hydroxydodecanoate, 3-hydroxydodecenoate,3-hydroxytetradecanoate, 3-hydroxyhexadecanoate, 3-hydroxyoctadecanoate,3-hydroxy-4-pentenoate, 4-hydroxybutyrate, 4-hydroxyvalerate,5-hydroxyvalerate, and 6-hydroxyhexanoate.

The copolymer can be poly 3-hydroxybutyrate-co-3-hydroxypropionate, poly3-hydroxybutyrate-co-4-hydroxybutyrate, poly3-hydroxybutyrate-co-3-hydroxyvalerate, poly3-hydroxybutyrate-co-3-hydroxyhexanoate, poly3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate, or poly3-hydroxybutyrate-co-3-hydroxyhexanoate-co-3-hydroxyoctanoate-co-3-hydroxydecanoate-co-3-hydroxydodecanotate-co-3-hydroxydodecenotate.

The 3-hydroxybutyrate can be present in the copolymer in a range ofabout 60 to 98 weight percent, about 70 to 98 weight percent, about 80to 98 weight percent, or about 90 to 98 weight percent.

The aliphatic polyester can include polybutylene succinate orpolybutylene succinate adipate.

The thermoplastic polyester can include an aromatic polyester.

The aromatic polyester can include a polyethylene terephthalate.

The polyethylene terephthalate can include a co-monomer.

The co-monomer can be an ether or amide or aliphatic monomer.

The aromatic polyester can be a polybutylene adipate/terephthalate or apolymethylene adipate/terephthalate.

The nucleant can include cyanuric acid.

The composition can include a polyolefin.

The polyolefin can be a polyethylene, polypropylene, or polybutylene.

In another aspect, the invention features an article that includes acomposition that includes a thermoplastic polyester or polyolefin, and anucleant. The nucleant includes a compound that includes anitrogen-containing heteroaromatic core.

In embodiments, the article can be in the form of a fiber, filament,rod, tube, or film.

In another aspect, the invention features a process that includesforming an article from a composition that includes a thermoplasticpolyester or polyolefin, and a nucleant. The nucleant includes acompound that includes a nitrogen-containing heteroaromatic core.

In embodiments, forming the article comprises molding or extruding thecomposition.

In another aspect, the invention features an article made by a processthat includes forming an article from a composition that includes athermoplastic polyester or polyolefin, and a nucleant. The nucleantincludes a compound that includes a nitrogen-containing heteroaromaticcore.

In another aspect, the invention features a composition that includes atleast one type of thermoplastic polyester and a nucleant comprising acompound of Formula 7 (described below), wherein R₁ is a hydrogen atomor an alkyl group having 1 to 4 carbon atoms, R₂ and R₃ are each ahydrogen atom or an alkyl group having 1 to 12 carbon atoms, M is agroup III or IV metal atom, and X is HO, O═, or (HO)₂. The compositioncan be substantially devoid of alkali-metal carboxylates, alkali metalβ-diketonates, alkali metal salts of β-ketoacetic esters, andpolyethylene terephthalates.

Embodiments can include one or more of the following features.

X can be OH, M can be Al, R₁ can be H, R₂ can be t-C₄H₉, and R₃ can bet-C₄H₉.

The thermoplastic polyester can be an aliphatic polyester.

The aliphatic polyester can be selected from the group consisting ofpolybutylene succinates, polycaprolactones, polyhydroxyalkanoates,polyglycolic acids, polylactic acids, and combinations thereof.

The aliphatic polyester can be a polyhydroxyalkanoate.

The polyhydroxyalkanoate can be a polyhydroxyalkanoate homopolymerselected from the group consisting of poly-3-hydroxybutyrate, polylacticacid, polyglycolic acid and poly-4-hydroxybutyrate.

The polyhydroxyalkanoate can be a copolymer of 3-hydroxybutyrate and atleast one co-monomer selected from the group consisting of3-hydroxypropionate, 3-hydroxyvalerate, 3-hydroxyhexanoate,3-hydroxyheptanoate, 3-hydroxyoctanoate, 3-hydroxynonaoate,3-hydroxydecanoate, 3-hydroxydodecanoate, 3-hydroxydodecenoate,3-hydroxytetradecanoate, 3-hydroxyhexadecanoate, 3-hydroxyoctadecanoate,3-hydroxy-4-pentenoate, 4-hydroxybutyrate, 4-hydroxyvalerate,5-hydroxyvalerate, and 6-hydroxyhexanoate.

The copolymer can be poly 3-hydroxybutyrate-co-3-hydroxypropionate, poly3-hydroxybutyrate-co-4-hydroxybutyrate, poly3-hydroxybutyrate-co-3-hydroxyvalerate, poly3-hydroxybutyrate-co-3-hydroxyhexanoate, poly3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate, or poly3-hydroxybutyrate-co-3-hydroxyhexanoate-co-3-hydroxyoctanoate-co-3-hydroxydecanoate-co-3-hydroxydodecanotate-co-3-hydroxydodecenotate.

The 3-hydroxybutyrate can be present in the copolymer in a range ofabout 60 to 98 weight percent, about 70 to 98 weight percent, about 80to 98 weight percent, or about 90 to 98 weight percent.

The aliphatic polyester can include polybutylene succinate orpolybutylene succinate adipate.

The thermoplastic polyester can include an aromatic polyester.

In another aspect, the invention features an article comprising acomposition that includes at least one type of thermoplastic polyesterand a nucleant comprising a compound of Formula 7, wherein R₁ is ahydrogen atom or an alkyl group having 1 to 4 carbon atoms, R₂ and R₃are each a hydrogen atom or an alkyl group having 1 to 12 carbon atoms,M is a group III or IV metal atom, and X is HO, O═, or (HO)₂. Thecomposition can be substantially devoid of alkali-metal carboxylates,alkali metal β-diketonates, alkali metal salts of β-ketoacetic esters,and polyethylene terephthalates.

In embodiments, the article can be in the form of a fiber, filament,rod, tube, or film.

In another aspect, the invention features a process that includesforming an article from a composition that includes at least one type ofthermoplastic polyester and a nucleant comprising a compound of Formula7, wherein R₁ is a hydrogen atom or an alkyl group having 1 to 4 carbonatoms, R₂ and R₃ are each a hydrogen atom or an alkyl group having 1 to12 carbon atoms, M is a group III or IV metal atom, and X is HO, O═, or(HO)₂. The composition can be substantially devoid of alkali-metalcarboxylates, alkali metal β-diketonates, alkali metal salts ofβ-ketoacetic esters, and polyethylene terephthalates.

In embodiments, forming the article can include molding or extruding thecomposition.

In still another aspect, the invention features an article made by aprocess that includes forming an article from a composition thatincludes at least one type of thermoplastic polyester and a nucleantcomprising a compound of Formula 7, wherein R₁ is a hydrogen atom or analkyl group having 1 to 4 carbon atoms, R₂ and R₃ are each a hydrogenatom or an alkyl group having 1 to 12 carbon atoms, M is a group III orIV metal atom, and X is HO, O═, or (HO)₂. The composition can besubstantially devoid of alkali-metal carboxylates, alkali metalβ-diketonates, alkali metal salts of β-ketoacetic esters, andpolyethylene terephthalates.

In yet another aspect, the invention features a method of fabricating athermoplastic composition. The method includes contacting athermoplastic polyester with a nucleant. The nucleant includes acompound that includes a nitrogen-containing heteroaromatic core.

Embodiments can include one or more of the following features.

The nitrogen-containing heteroaromatic core can be a pyridine,pyrimidine, pyrazine, pyridazine, triazine, or imidazole.

The compound can have a chemical formula of Formula 1, Formula 2,Formula 3, Formula 4, Formula 5, or Formula 6 (all of which aredescribed in detail below) and combinations thereof, wherein each R1 isindependently H, NR²R², OH, OR², SR², SOR², SO₂R², CN, COR², CO₂R²,CONR²R², NO₂, F, Cl, Br, or I; and each R² is independently H or C₁-C₆alkyl.

The nucleant can include cyanuric acid.

In an additional aspect, the invention features a method of fabricatinga thermoplastic composition. The method includes contacting athermoplastic polyester having a melting temperature at or below about260° C., e.g., at or below about 250° C., or at or below about 200° C.,or in a range of about 240-260° C., with methylbenzylidene sorbitol ordimethylbenzylidene sorbitol dissolved in a solvent; melting thethermoplastic polyester at or below about 260° C., e.g., at or belowabout 250° C., or at or below about 200° C., or in a range of about240-260° C.; and cooling the thermoplastic polyester, to therebyfabricate the thermoplastic composition.

Embodiments can include one or more of the following features.

The thermoplastic polyester can be a polyhydroxyalkanoate.

The polyhydroxyalkanoate can be a polyhydroxyalkanoate homopolymerselected from the group consisting of poly-3-hydroxybutyrate, polylacticacid, polyglycolic acid and poly-4-hydroxybutyrate.

The polyhydroxyalkanoate can be a copolymer of 3-hydroxybutyrate and atleast one co-monomer selected from the group consisting of3-hydroxypropionate, 3-hydroxyvalerate, 3-hydroxyhexanoate,3-hydroxyheptanoate, 3-hydroxyoctanoate, 3-hydroxynonaoate,3-hydroxydecanoate, 3-hydroxydodecanoate, 3-hydroxydodecenoate,3-hydroxytetradecanoate, 3-hydroxyhexadecanoate, 3-hydroxyoctadecanoate,3-hydroxy-4-pentenoate, 4-hydroxybutyrate, 4-hydroxyvalerate,5-hydroxyvalerate, and 6-hydroxyhexanoate.

The copolymer can be poly 3-hydroxybutyrate-co-3-hydroxypropionate, poly3-hydroxybutyrate-co-4-hydroxybutyrate, poly3-hydroxybutyrate-co-3-hydroxyvalerate, poly3-hydroxybutyrate-co-3-hydroxyhexanoate, poly3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate, or poly3-hydroxybutyrate-co-3-hydroxyhexanoate-co-3-hydroxyoctanoate-co-3-hydroxydecanoate-co-3-hydroxydodecanotate-co-3-hydroxydodecenotate.

The 3-hydroxybutyrate can be present in the copolymer in a range ofabout 60 to 98 weight percent, about 70 to 98 weight percent, about 80to 98 weight percent, or about 90 to 98 weight percent.

Embodiments may have one or more of the following advantages.

In some embodiments, nucleants suitable for use with semicrystallinethermoplastics, e.g., thermoplastic polyesters, are provided, which canimprove or increase the crystallization rate of the thermoplastics.

In other embodiments, a thermoplastic composition is provided, which hasan improved or increased crystallization rate and/or other improvedphysical properties, e.g., increased mechanical strength.

In still other embodiments, an improved method of fabricating athermoplastic composition, e.g., a composition comprising athermoplastic polyester (e.g., PHA) and at least one nucleant describedherein, is provided.

In yet other embodiments, articles that include a thermoplasticcomposition described herein are provided, which have improved physicaland/or economic characteristics.

Other features and advantages of the invention will be apparent from thefollowing detailed description, and from the claims.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of the present invention, suitable methods andmaterials are described below. All publications, patent applications,patents, and other references mentioned herein are incorporated byreference in their entirety. In case of conflict, the presentspecification, including definitions, will control. In addition, thematerials, methods, and examples are illustrative only and not intendedto be limiting.

DETAILED DESCRIPTION

The invention provides nucleants that can be added to any thermoplastic.For example, the nucleants described herein can be added tothermoplastic polyesters, e.g., polyhydroxyalkanoates (PHA), polylacticacids (PLA), polybutylene succinates (PBS), polycaprolactones (PCL),polyethylene terephthalates (PET), PET copolymers (e.g., PET adipates,PET succinate adipates, and the like), polybutylene terepthalates (PBT),and PBT copolymers (e.g. PBT adipates, PBT succinate adipates, and thelike). The nucleants described herein can also be added to polyolefinssuch as, for example, polypropylene. Methods for using the nucleants arealso provided. The invention also includes thermoplastic compositionsthat include the nucleants, which can be used to create a wide array ofuseful articles.

I. Nucleants

The terms “nucleant(s)” and “nucleating agent(s)” refer to compoundsthat can be added to a thermoplastic (e.g., thermoplastic in a dissolvedor melted state) to introduce one or more nucleation sites forcrystallization of the thermoplastic.

In certain embodiments, the nucleant can have a nitrogen containingheteroaromatic core. Some examples of suitable heteroaromatic coresinclude pyridines, pyrimidines, pyrazines, pyridazine, triazines, andimidazoles. The heteroaromatic core can be substituted, for example,with polar or non-polar groups. For example, a nucleant can have one ofthe following formulae:

wherein each R¹ is independently H, NR²R², OR², OH, SR², SOR², SO₂R²,CN, COR², CO₂R², CONR²R², NO₂, or halo (e.g., F, Cl, Br, or I); and eachR² is independently H or C₁-C₆ alkyl. Exemplary species of suitablenucleating agents include, but are by no means limited to, uracil or aderivative thereof, thymine or a derivative thereof, and nitroimidazole.

In some embodiments, a nucleant can be cyanuric acid(1,3,5-triazine-2,4,6-triol; “CyA”), which has the following formula:

In certain embodiments, the nucleant can be at least one of basicpolyvalent metal salts of cyclic organophosphoric esters of thefollowing general formula:

wherein R₁ represents a hydrogen atom or an alkyl group having 1 to 4carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, butyl, sec-butylor isobutyl), R₂ and R₃ each represent a hydrogen atom or an alkyl grouphaving 1 to 12 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl,butyl, sec-butyl, tert-butyl, amyl, tert-amyl, hexyl, heptyl, octyl,isooctyl, tert-octyl, 2-ethylhexyl, nonyl, isononyl, decyl, isodecyl,undecyl, dodecyl and tert-dodecyl), M represents a group III or IV metalatom of the periodic table, and X represents HO— when M represents agroup III metal atom of the periodic table and X represents O═ or (HO)₂—when M represents a group IV metal atom of the periodic table.

For example, in certain embodiments, the nucleant can have the generalformula of Formula 7, wherein X is OH, and M is Al. In such embodiments,R₁ can be H, R₂ can be t-C₄H₉, and R₃ can be t-C₄H₉; or R₁ can be H, R₂can be CH₃, and R₃ can be t-C₄H₉; or R₁ can be CH₃, R₂ can be t-C₄H₉,and R₃ can be t-C₄H₉. As used herein, an “aluminum hydroxy diphosphate”(AHD) is a compound having the general formula of Formula 7, wherein Xis OH, M is Al, R₁ is H, R₂ is t-C₄H₉, and R₃ is t-C₄H₉.

In other embodiments, the nucleant can be a compound that includesmethylbenzylidene sorbitol (MBS) and/or dimethylbenzylidene sorbitol(DMBS). MBS and DMBS are commercially available, for example, fromMilliken Chemicals as Millad® 3940 and 3988, respectively. Benzylidenesorbitols, such as MBS and DMBS, are known as clarifiers and havemelting points above 200° C. Typically, clarifiers are mixed with apolymer (such as polypropylene) and melted (i.e., at temperatures above200° C.). The plastic/clarifier mixture is then cooled. The clarifiercrystallizes quickly during cooling, and the crystals act as nucleantfor the polymer.

The typical way in which clarifiers such as MBS and DMBS are used is notcompatible with certain thermoplastic polyesters, e.g., PHAs, becausethe temperature needed to melt MBS and DMBS is above the decompositiontemperature of those thermoplastics. However, applicants have found thatMBS and DMBS are effective nucleants for such thermoplastics ifdispersed in the thermoplastic at a temperature below the decompositiontemperature of the thermoplastic. This process makes heating thethermoplastic to the melting temperature of MBS or DMBS unnecessary.

Nucleants can be provided in a variety of forms. For example, thenucleant can be included in a dry nucleant composition, e.g., a granularor powder composition in which the particle size of the nucleant hasbeen reduced to less than about 100 microns, e.g., less than about 10microns, or less than about 5 microns. Alternatively, the nucleant canbe included in a nucleant formulation. As used herein, a “nucleantformulation” refers to a formulation that includes a nucleant (ormultiple nucleants) described herein dissolved or dispersed in anucleant solvent. The term “nucleant solvent” means a liquid that eitherdissolves the nucleant or acts as a medium in which the nucleant isdispersed and that does not intolerably reduce the nucleant'seffectiveness as a nucleant. Nucleant solvents for use in the inventioninclude but are not limited to common solvents and other liquids such asplasticizers. A dry nucleant composition and nucleant formulation canoptionally include one or more compound useful in the production ofthermoplastics, e.g., a plasticizer, antioxidant, ultravioletstabilizer, lubricant, pigment, flame retardant, and/or antistaticagent.

II. Thermoplastic Compositions

Nucleants can be used to form a thermoplastic composition containing oneor more nucleants and one or more semicrystalline thermoplastics.Examples of thermoplastics include polyesters, acrylics, cellulosics,polyamides, polyolefins, polystyrenes, and polyvinyls. Examples ofthermoplastic polyesters include, e.g., PHA, PET, polybutyleneterephthalate (PBT), and various copolyesters of PET and PBT. Some suchpolyesters may be produced by polymerizing aliphatic diacids, diols, orhydroxy acids to produce copolyesters that are biodegradable orcompostable; and various aliphatic polyesters and copolyesters derivedfrom dibasic acids, e.g., succinic acid, glutaric acid, adipic acid,sebacic acid, azealic acid, or their derivatives, e.g., alkyl esters,acid chlorides, or their anhydrides; diols such as ethylene glycol,propylene glycol, 1,4-butanediol, 1,6-hexanediol, or1,4-cyclohexanedimethanol, or their cyclic oxides such as ethyleneoxide, propylene oxide, or THF; lactic acid or lactide, or glycolic acidor glycolide.

Methods for making and using thermoplastic compositions are well knownto those of skill in the art. Skilled practitioners will appreciate thatthe nucleants of the present invention can be used with these and anyother thermoplastic (or mixtures of such thermoplastics, e.g., mixturesof at least two, e.g., at least three, four, five, seven, or tenthermoplastics), regardless of whether the thermoplastic is natural orsynthetic, or biodegradable or non-biodegradable. Further, as is knownto skilled practitioners, a thermoplastic composition can contain one ormore additive, e.g., a filler, plasticizer, antioxidant, ultravioletstabilizer, lubricant or slip agent, pigment, transesterificationcatalyst or other cross linking agent, flame retardant, and/orantistatic agent.

The thermoplastics may be homopolymers, copolymers, or any combinationof homopolymers and copolymers, e.g., two homopolymers, two copolymers,or one homopolymer and one copolymer. The term “homopolymer” refers topolymers having the same monomer units. The term “copolymer” refers topolymers having two or more different monomer units (also referred toherein as comonomers or comonomer units) and includes, e.g.,alternating, block, and random copolymers.

The nucleants of the invention are suitable for use with PHAs. Examplesof PHA monomer units include 3-hydroxybutyrate, 3-hydroxypropionate,3-hydroxyvalerate, 3-hydroxyhexanoate, 3-hydroxyheptanoate,3-hydroxyoctanoate, 3-hydroxynonaoate, 3-hydroxydecanoate,3-hydroxydodecanoate, 3-hydroxydodecenoate, 3-hydroxytetradecanoate,3-hydroxyhexadecanoate, 3-hydroxyoctadecanoate, 3-hydroxy-4-pentenoate,4-hydroxybutyrate, 4-hydroxyvalerate, 5-hydroxyvalerate, and6-hydroxyhexanoate.

The PHA can be a homopolymer (i.e., all monomer units are the same).Examples of PHA homopolymers include poly 3-hydroxyalkanoates (e.g.,poly 3-hydroxypropionate, poly 3-hydroxybutyrate, poly3-hydroxyhexanoate, poly 3-hydroxyheptanoate, poly 3-hydroxyoctanoate,poly 3-hydroxydecanoate, poly 3-hydroxydodecanoate), poly4-hydroxyalkanoates (e.g., poly 4-hydroxybutyrate), poly5-hydroxyalkanoates (e.g., poly 5-hydroxypentanoate), and poly6-hydroxyalkanoates (e.g., poly 6-hydroxyhexanoate).

In certain embodiments, the PHA can be a copolymer (i.e., the PHA cancontain two or more different monomer units). Examples of PHA copolymersinclude poly 3-hydroxybutyrate-co-3-hydroxypropionate, poly3-hydroxybutyrate-co-4-hydroxybutyrate, poly3-hydroxybutyrate-co-4-hydroxypentenoate, poly3-hydroxybutyrate-co-3-hydroxyvalerate, poly3-hydroxybutyrate-co-3-hydroxyhexanoate, poly3-hydroxybutyrate-co-4-hydroxyvalerate, poly3-hydroxybutyrate-co-6-hydroxyhexanoate, poly3-hydroxybutyrate-co-3-hydroxyheptanoate, poly3-hydroxybutyrate-co-3-hydroxyoctanoate, poly3-hydroxybutyrate-co-3-hydroxydecanoate, poly3-hydroxybutyrate-co-3-hydroxydodecanotate, poly3-hydroxybutyrate-co-3-hydroxyoctanoate-co-3-hydroxydecanoate, poly3-hydroxydecanoate-co-3-hydroxyoctanoate, and poly3-hydroxybutyrate-co-3-hydroxyoctadecanoate. Although examples of PHAcopolymers having two different monomer units have been provided, thePHA can have more than two different monomer units (e.g., threedifferent monomer units (e.g., poly3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate, whereinthe 3-hydroxybutyrate component is at least about 70 weight percent,e.g., at least about 80 weight percent, at least about 90 weightpercent, or at least about 96 weight percent of the total polymer), fourdifferent monomer units, five different monomer units, six differentmonomer units (e.g., poly3-hydroxybutyrate-co-3-hydroxyhexanoate-co-3-hydroxyoctanoate-co-3-hydroxydecanoate-co-3-hydroxydodecanotate-co-3-hydroxydodecenotatewherein the 3-hydroxybutyrate component is at least about 80 weightpercent, e.g., at least about 90 weight percent, or at least about 96weight percent of the total polymer), seven different monomer units,eight different monomer units, nine different monomer units, tendifferent monomer units, or more than ten different monomer units).

PHAs can be derived from biomass, such as plant biomass and/or microbialbiomass (e.g., bacterial biomass, yeast biomass, fungal biomass).Biomass-derived PHA can be formed, for example, via enzymaticpolymerization of the monomer units. The biomass can be formed of one ormore of a variety of entities. Such entities include, for example,microbial strains for producing PHAs (e.g., Alcaligenes eutrophus(renamed as Ralstonia eutropha), Bacillus, Alcaligenes latus,Azotobacter, Aeromonas, Comamonas, Pseudomonads), genetically engineeredorganisms, for producing PHAs (e.g., Pseudomonas, Ralstonia, Escherichiacoli, Klebsiella), yeasts for producing PHAs, and plant systems forproducing PHAs. Such entities are disclosed, for example, in Lee,Biotechnology & Bioengineering 49:1-14 (1996); Braunegg et al., (1998),J. Biotechnology 65: 127-161; Madison, L. L. and Huisman, G. W. (1999),Metabolic Engineering of Poly(3-Hydroxyalkanoates): From DNA to Plastic.Microbiol. Mol. Biol. Rev. 63, 21-53; and Snell and Peoples 2002,Metabolic Engineering 4: 29-40, which are hereby incorporated byreference.

Alternatively, the PHA can be derived by chemical synthesis, such as bythe ring opening polymerization of β-lactone monomers using variouscatalysts or initiators such as aluminoxanes, distannoxanes, oralkoxy-zinc and alkoxy-aluminum compounds (see Agostini, D. E. et al.Polym. Sci., Part A-1, 9: 2775-2787 (1971); Gross, R. A. et al.,Macromolecules 21:2657-2668 (1988); Dubois, P. I. et al.,Macromolecules, 26:4407-4412 (1993); LeBorgne, A. and Spassky, N.Polymer, 30:2312-2319 (1989); Tanahashi, N. and Doi, Y. Macromolecules,24:5732-5733 (1991); Hori, Y. M. et al., Macromolecules, 26:4388-4390(1993); Kemnitzer, J. E. et al., Macromolecules, 26:1221-1229 (1993);Hori, Y. M. et al., Macromolecules, 26:5533-5534 (1993); Hocking, P. J.and Marchessault, R. H., Polym Bull., 30: 163-170 (1993). The PHA canalso be obtained by condensation polymerization of esters (see Hubbs, J.C. and Harrison, M. N. U.S. Pat. No. 5,563,239) or by chemoenzymaticmethods (see Xie, et al., Macromolecules, 30:6997-6998 (1997)).

The nucleants are also suitable for use with PLA and polyglycolic acid.PLA and polyglycolic acid are often prepared by either condensationpolymerization of the free acids or by catalytic, ring-openingpolymerization of the dilactones. PLA and polyglycolic acid arebiodegradable and degrade to lactic acid and glycolic acid,respectively.

The nucleants are also suitable for use with other biodegradablepolymers, including PBS, polybutylene succinate adipate (PBSA), andmixtures thereof. A PBS polymer is generally prepared by thecondensation polymerization of a glycol and a dicarboxylic acid or anacid anhydride thereof. A PBS polymer may either be a linear polymer ora long-chain branched polymer. A long-chain branched PBS polymer isgenerally prepared by using an additional polyfunctional componentselected from the group consisting of trifunctional or tetrafunctionalpolyols, oxycarboxylic acids, and polybasic carboxylic acids. A PBSApolymer is generally prepared by the polymerization of at least onealkyl glycol and more than one aliphatic multifunctional acid.

The nucleants are also suitable for use with PCL. PCL is a biodegradablesynthetic aliphatic polyester and is generally made by the ring-openingpolymerization of caprolactone. PCL may be obtained from any commercialsource, e.g., Union Carbide (UCC).

The nucleants can also be used with PET and/or PET that is modified tobe biodegradable (“modified PET”). PET is commonly prepared by thereaction of ethylene glycol with a terephthalate ester such as dimethylterephthalate or, occasionally, with terephthalic acid. Modified PET isPET that contains co-monomers, e.g., ether, amide, or aliphaticmonomers, which provide one or more linkages susceptible to hydrolysis.An example of a commercially available modified PET is Biomax™,available from DuPont. Examples of modified PBTs include polybutyleneadipate/terephthalate (PBAT) and polytetramethyleneadipate/terephthalate (PTMAT). Examples of commercially available PBTsare Ecoflex™ available from BASF, and Eastar™, available from EastmanChemical Company.

The nucleants of the present invention may also be used withpolyolefins. Any polyolefin capable of being fabricated into an article,such as a microfiber, is suitable for use in the present invention.Exemplary polyolefins are homopolymers and copolymers comprisingrepeating units formed from one or more aliphatic hydrocarbons,including ethylene, propylene, butene, pentene, hexene, heptene, octene,1,3-butadiene, and 2-methyl-1,3-butadiene. The polyolefins may be highor low density and may be generally linear or branched chain polymers.Methods of forming polyolefins such as polypropylene are known to thoseskilled in the art.

III. Production and Processing of Thermoplastic Compositions

Thermoplastic compositions can be produced using any art-known methodthat includes adding a nucleant to a thermoplastic. The nucleant can beadded to a thermoplastic as a dry nucleant composition and/or as anucleant formulation. If the nucleant is added as a dry nucleantcomposition, e.g., as granules or as powder, the particle size is notcritical from the standpoint of the qualitative effect on nucleation. Ingeneral, however, small particle size (e.g., less than about 100microns) allows intimate mixing and thorough distribution within athermoplastic. Particle size of the nucleant can be minimized to ensureuniform dispersion in the polymer and a sufficient number of nucleationsites. For example, U.S. Pat. No. 5,973,100 indicates that nucleationcan occur if the particle size of a nucleant is below about 700 micronsand increases in efficacy as the particle size is further reduced. Forqualitative evaluation of the effectiveness of a chemical species innucleating a polymer, a high loading (e.g., greater than 1 weightpercent) of nucleant with a relatively large particle size is adequate.In commercially useful polymer formulations, further reduction in theparticle size of the nucleant can increase the nucleant efficacy and canminimize defects and flaws in the polymer. For high effectiveness,particle size below about 5 microns, e.g., below about 2 microns, can beused. Reduction of the particle size of the nucleant is typicallyachieved by mechanical methods, such as grinding.

The nucleants can be added to a thermoplastic prior to, during, and/orafter melting or dissolving the thermoplastic, using any art-knownmixing means, e.g., by mechanically admixing nucleants andthermoplastics (e.g., by stirring, shaking, or subjecting the mixture toultrasound). For example, a solvent dispersion process can be employed.In such a process, thermoplastic is dissolved in a solvent and nucleantis dispersed therein, e.g., by agitating the mixture, to form ahomogeneous thermoplastic/nucleant mixture. In another process, athermoplastic is melted and the nucleant is dispersed therein under highsheer. In still another process, nucleant is dispersed in a liquidcarrier, e.g., a plasticizer, and mixed with a thermoplastic, e.g., athermoplastic dissolved in a solvent or in a melted state.

The nucleant is combined with the thermoplastic in an amount effectiveto increase the crystallization rate and/or final crystallinity of thethermoplastic, e.g., as reflected by an increased temperature ofcrystallization by differential scanning calorimetry (DSC). Skilledpractitioners will appreciate that a nucleant of the present inventioncan be added to a thermoplastic in any desired amount. Optimal amountsto be added will depend on various factors known to skilledpractitioners, e.g., cost, desired physical characteristics of thethermoplastic (e.g., mechanical strength), and the type of processingbeing performed (raising, e.g., considerations of line speeds, cycletimes, and other processing parameters). Also to be considered iswhether the thermoplastic composition includes other additives, e.g.,plasticizers, stabilizers, pigments, fillers, reinforcing agents, and/ormold release agents. In general, however, a nucleant can be included ina thermoplastic composition such that the composition contains about0.005% by weight to about 20%, e.g., about 0.05% to about 10%, about0.5% to about 5% nucleant, based on the total weight of the composition.In certain embodiments of the present invention, the compositioncontains about 1% to about 10%, e.g., about 1% to about 5% nucleant. Incertain embodiments, the composition contains about 0.1% to about 2.0%nucleant.

Without wishing to be bound by theory, it is believed that the nucleantsof the present invention can exert their effect, for example, when athermoplastic composition is heated to a temperature above thecrystalline melting point of the thermoplastic and then cooled to atemperature below the crystalline melting point of the thermoplastic. Itis within the skilled practitioner's abilities to select the optimumrate of cooling of the composition from a temperature above thecrystalline melting point to temperatures below such point. In selectingthe optimum rate of cooling, skilled practitioners may consider the kindof thermoplastic and nucleant employed, the amount of nucleant presentin the composition, and the crystalline structure desired in thethermoplastic product. Thermoplastic compositions nucleated inaccordance with this invention may crystallize at higher rates (e.g.,due to more centers of nucleation) than do otherwise similarcompositions that do not include an added nucleant.

Optionally, an additive can be included in the thermoplasticcomposition. The additive can be any compound known to those of skill inthe art to be useful in the production of thermoplastics. Exemplaryadditives include, e.g., plasticizers (e.g., to increase flexibility ofa thermoplastic composition), antioxidants (e.g., to protect thethermoplastic composition from degradation by ozone or oxygen),ultraviolet stabilizers (e.g., to protect against weathering),lubricants (e.g., to reduce friction), pigments (e.g., to add color tothe thermoplastic composition), clarifiers, flame retardants, fillers,and antistatic agents. It is well within the skilled practitioner'sabilities to determine whether an additive should be included in athermoplastic composition and, if so, the amount that should be added tothe composition.

For the fabrication of useful articles, a thermoplastic composition canbe created at a temperature above the crystalline melting point of thethermoplastic but below the decomposition point of at least one (e.g.,all) of the ingredients of the composition. Alternatively, a pre-madethermoplastic composition of the present invention is simply heated tosuch temperature. While in molten condition, the composition isprocessed into a desired shape, e.g., a fiber, filament, film, sheet,rod, tube, or other shape. Such processing can be performed using anyart-known technique, e.g., extrusion, injection molding, compressionmolding, blow molding, film blowing, fiber spinning, blown fiber, spunbonded fiber coextrusion, paper coating, calendering, rotationalmolding, casting, or thermoforming. The articles so formed aresubsequently cooled to set the shape and induce crystallization.

The thermoplastic compositions of the present invention can be used tocreate a wide variety of useful articles, e.g., automotive, consumerdisposable (including hygiene articles, wet wipes and disposable medicalproducts), consumer durable, construction, electrical, medical, andpackaging articles. Such articles are also within the present invention.

For example, the article can be a film. A film is an extremely thincontinuous piece of a substance having a high length to thickness ratioand a high width to thickness ratio. The film can be liquid impervious.Such films can be included in a variety of disposable productsincluding, e.g., sanitary garments, e.g., disposable diapers, femininehygiene products (such as an intralabial device) and the like,shrink-wrapping (e.g., food wraps, consumer product wraps, pallet and/orcrate wraps, and the like), or bags (grocery bags, food storage bags,sandwich bags, garbage bags, and the like).

The article can be a sheet. A sheet is a very thin continuous piece of asubstance, having a high length to thickness ratio and a high width tothickness ratio, wherein the material is thicker than 0.254 mm. Sheetingshares many of the same characteristics as film in terms of propertiesand manufacture, with the exception that sheeting is stiffer, and has aself-supporting nature. Such differences in stiffness and support resultin some modification of the manufacturing methods.

The article can be a fiber. A fiber is a flexible, homogeneous bodyhaving a high length-to-width ratio and a small cross section. Fibersare useful, e.g., as textiles in yarns for garments. Fibers are alsouseful for manufacturing lightweight fibrous materials useful inagricultural applications to protect, promote, or control plant growth.Fibers are also useful for making non-woven articles such as wet wipesor components of diapers and feminine hygiene articles. They are alsouseful to make green house thermal screens, crop row covers, turfcovers, weed barriers and hydroponic articles.

The article can be a foam. A foam is a thermoplastic whose apparentdensity has been substantially decreased by the presence of numerouscells distributed throughout its bulk. Foams can be used to make, e.g.,packaging (e.g., hot and cold food packaging containers), cushioning(e.g., comfort cushioning and packing material), insulation, andstructural components.

The article can be a molded article. A molded article is an articleformed from thermoplastic polyesters that are, for example, injected,compressed, or blown by means of a gas into shape defined by a femalemold. These objects can be solid objects like toys, or hollow likebottles and containers.

The article can be a nonwoven. A nonwoven is a porous, textile likematerial, usually in flat sheet form, composed primarily, or entirely,of fibers assembled in webs that are manufactured by processes otherthan spinning, weaving, or knitting.

The article can be an elastomer. An elastomer is a material thatexhibits both long-range deformability on application of stress andessentially complete recovery on removal. Elastomers can also be used inblend formulations with other polymers (or copolymers) to increaseimpact strength and toughness in stiffer materials.

The article can be an adhesive. An adhesive is a material that joins twoother materials, called adherends, together. Thermoplastic compositionsmay be processed into a variety of adhesives, including, e.g., hot melt,solution, dispersion and pressure sensitive adhesives.

The article can be a disposable personal care product. For example, thearticle can be a compostable absorbent article comprising a liquidpervious topsheet, a liquid impervious backsheet that includes a filmdescribed herein, and an absorbent core positioned between the topsheetand backsheet. Such articles include infant diapers, adult incontinentbriefs and pads, and feminine hygiene pads and liners. Additionalpersonal care products that can include the thermoplastics of thepresent invention include personal cleansing wipes; disposable healthcare products such as bandages, wound dressings, wound cleansing pads,surgical gowns, surgical covers, surgical pads; and other institutionaland health care disposables, such as gowns, wipes, pads, and beddingitems (e.g., sheets, pillowcases, and foam mattress pads).

In some embodiments, the thermoplastic compositions of the presentinvention can be used, e.g. for blending with other materials includingthermoplastic starches, polyglycolic acid polymers, polyvinyl alcoholpolymers, polylactic acid polymers, cellulosic materials or syntheticbiodegradable polymers.

The invention will be further described in the following examples, whichdo not limit the scope of the invention defined by the claims.

EXAMPLES Example 1 Use of Cyanuric Acid, AHD, MBS, and DMBS as NucleantsMethods

Example 1 demonstrates that cyanuric acid is an effective nucleator ofpoly 3-hydroxybutyrate (P3HB), poly3-hydroxybutyrate-co-11%-4-hydroxybutyrate (P3HB-co-11-4HB), poly3-hydroxybutyrate-co-5%-3-hydroxyhexanoate (P3HB-co-5-3HH), poly3-hydroxybutyrate-co-8%-3-hydroxyvalerate (P3HB-co-8-3HV), poly4-hydroxybutyrate (P4HB), PLA, PET, and polypropylene. The Example alsodemonstrates that AHD nucleates P3HB-co-11-4HB. Further, the Exampledemonstrates that MBS and DMBS nucleate P3HB-co-11-4HB.

Cyanuric acid (CAS #[108-80-5], 1,3,5-triazine-2,4,6-triol) was reagentgrade (98%, mp>360° C., from Aldrich Chemical). AHD was separated fromcommercial NA-21 (Amfine Chemicals) by stirring 4 grams of NA-21 in 100ml of reagent grade methanol for several hours. The slurry was filteredand washed with methanol. The remaining solid was dried in vacuo at 65°C. The supernatant was evaporated on a hotplate followed by drying invacuo at 65° C. to yield a white solid. DSC analysis showed that thecomplete absence of melting endotherms of 94 and 216° C. (carboxylatesalt plus free carboxylic acid) and no additional melting up to 300° C.This indicates complete removal of added components. Benzylidenesorbitol (BS; Millad 3905), MBS (Millad 3940) and DMBS (Millad 3988) wasobtained from Milliken Chemical. Boron nitride, Grade NX1, was obtainedfrom GE Advanced Ceramics (Cleveland, Ohio).

Polymer films containing nucleant were prepared by either a solutionmethod (Method A) or melt blending (Method B), as described below.

Polymer samples (ca. 10 mg) were analyzed by Differential ScanningCalorimetry (TA Instruments, Inc. DSC Model Q100) using the followingtemperature program: Heat at 50° C./min to Tmax. Hold for 3 minutes.Cool at 10° C./minute to 0° C. (except for P4HB, which was cooled to −70C). The thermograms were analyzed with TA Universal Analysis software.Tmax is 200° C. for P3HB, P3HB-co-8-3HV and P3HB-co-5-3HH, 185° C. forP3HB-co-11-4HB, 125° C. for P4HB, and 280° C. for PET. The shift of peaktemperature of the crystallization exotherm is taken as a measure of theeffectiveness of a given nucleant. The greater the upward shift intemperature, the more effective the nucleant.

Method A:

Polymer films containing nucleant were prepared by mixing 8 grams of a2.5% (w/w) solution of polymer in reagent grade Chloroform with 4 mg ofnucleant. The mixture was ultrasonically dispersed (Heat Systems, Inc,Ultrasonic Processor XL) using a power level of 5 for 2 minutes (5seconds on, 1 second off). The dispersion was poured into 10 cm diameterAluminum dishes and allowed to air dry followed by overnight removal ofthe last traces of solvent at about 65° C. under vacuum.

Method B:

Two grams of dried polymer and 20 mg of ground nucleant were mixed at270° C. for 4 minutes in a small scale heated melt mixer (Model LMM,Laboratory Mixing Molder, Atlas Electric Devices, Chicago, Ill.).

Results

The results obtained are summarized in Table 1, below. Controlexperiment 1 shows the crystallization of P3HB polymer. The addition ofboron nitride (commonly known as the best available nucleant for PHB),Control 2, results in a significant increase in the peak exothermtemperature to 107.6 from 62.8° C. Experimental example 1 shows thatcyanuric acid increases the crystallization exotherm to an even higher118.4° C.

Control 3 shows the crystallization of P3HB-co-11-4HB copolymer. Theaddition of boron nitride (Control 4) shows that it does not have anysignificant effectiveness in nucleating these copolymers. Experimentalexamples 2 through 6 show four effective nucleants, cyanuric acid, AHD,MBS and DMBS.

Control experiment 5 shows the crystallization of P3HB-co-5-3HHcopolymer. Control experiment 6 shows this polymer nucleated with boronnitride. Experimental example 7, with cyanuric acid, shows an almost 50°C. increase in peak exotherm temperature and that it is more effectivethan boron nitride.

Control experiments 7 and 8 show the crystallization of P3HB-co-8-3HVcopolymer and nucleated with boron nitride, respectively. Experimentalexample 8 shows that cyanuric acid is, again, even more effective withthis polymer.

Control experiment 9 and Experimental example 9 show that cyanuric acidis an effective nucleant for P4HB.

Control experiment 10 and Experimental example 10 show that cyanuricacid is an effective nucleant for PET.

Control experiment 11 and Experimental example 11 show that cyanuricacid is an effective nucleant for PLA, and is more effective than boronnitride.

Control experiment 13 and Experimental example 12 show that cyanuricacid nucleates polypropylene.

TABLE 1 Evaluation of Nucleants in Thermoplastics Experiment PolymerMethod Nucleant Tcr* CONTROL 1 P3HB A none 62.8 CONTROL 2 P3HB A BN107.6 EXAMPLE 1 P3HB A CyA 118.4 CONTROL 3 P3HB-co-11-4HB A none noneCONTROL 4 P3HB-co-11-4HB A BN none EXAMPLE 2 P3HB-co-11-4HB A CyA 69.7EXAMPLE 3 P3HB-co-11-4HB A AHD 58.9 EXAMPLE 4 P3HB-co-11-4HB A BS noneEXAMPLE 5 P3HB-co-11-4HB A MBS 63.8 EXAMPLE 6 P3HB-co-11-4HB A DMBS 40.7CONTROL 5 P3HB-co-5-3HH A none 49.7 CONTROL 6 P3HB-co-5-3HH A BN 78.3EXAMPLE 7 P3HB-co-5-3HH A CyA 99.0 CONTROL 7 P3HB-co-8-3HV A none 66.9CONTROL 8 P3HB-co-8-3HV A BN 92.5 EXAMPLE 8 P3HB-co-8-3HV A CyA 102.3CONTROL 9 P4HB A none 10.5 EXAMPLE 9 P4HB A CyA 15.6 CONTROL 10 PET nonenone 208.3 EXAMPLE 10 PET B CyA 212.7 CONTROL 11 PLA none none CONTROL12 PLA A BN 95.6 EXAMPLE 11 PLA A CyA 102.3 CONTROL 13 Polypropylene Bnone 118.8 EXAMPLE 12 Polypropylene B CyA 120.8 *Tcr is the peaktemperature for crystallization during cooling.

Other embodiments are within the scope of the following claims.

1. A composition comprising: a thermoplastic polyester; and a nucleanthaving a chemical formula selected from the group consisting of:

and combinations of any two or more thereof; wherein: each R¹ isindependently H, NR²R², OH, OR², SR², SOR², SO₂R², CN, COR², CO₂R²,CONR²R², NO₂, F, Cl, Br, or I; and each R² is independently H or C₁-C₆alkyl.
 2. The composition of claim 1, wherein the composition comprisesa thermoplastic polyester.
 3. The composition of claim 2, wherein thethermoplastic polyester comprises an aliphatic polyester.
 4. Thecomposition of claim 3, wherein the aliphatic polyester is selected fromthe group consisting of polybutylene succinates, polycaprolactones,polyhydroxyalkanoates, polyglycolic acids, polylactic acids, andcombinations of any two or more thereof.
 5. The composition of claim 3,wherein the aliphatic polyester comprises a polyhydroxyalkanoate.
 6. Thecomposition of claim 5, wherein the polyhydroxyalkanoate is apolyhydroxyalkanoate homopolymer selected from the group consisting ofpoly-3-hydroxybutyrate, polylactic acid, polyglycolic acid, andpoly-4-hydroxybutyrate.
 7. The composition of claim 5, wherein thepolyhydroxyalkanoate is a copolymer of 3-hydroxybutyrate and at leastone co-monomer selected from the group consisting of3-hydroxypropionate, 3-hydroxyvalerate, 3-hydroxyhexanoate,3-hydroxyheptanoate, 3-hydroxyoctanoate, 3-hydroxynonaoate,3-hydroxydecanoate, 3-hydroxydodecanoate, 3-hydroxydodecenoate,3-hydroxytetradecanoate, 3-hydroxyhexadecanoate, 3-hydroxyoctadecanoate,3-hydroxy-4-pentenoate, 4-hydroxybutyrate, 4-hydroxyvalerate,5-hydroxyvalerate, and 6-hydroxyhexanoate.
 8. The composition of claim7, wherein the copolymer is poly3-hydroxybutyrate-co-3-hydroxypropionate, poly3-hydroxybutyrate-co-4-hydroxybutyrate, poly3-hydroxybutyrate-co-3-hydroxyvalerate, poly3-hydroxybutyrate-co-3-hydroxyhexanoate, poly3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate, or poly3-hydroxybutyrate-co-3-hydroxyhexanoate-co-3-hydroxyoctanoate-co-3-hydroxydecanoate-co-3-hydroxydodecanotate-co-3-hydroxydodecenotate.9. The composition of claim 7, wherein the 3-hydroxybutyrate is presentin the copolymer in a range of about 60 to 98 weight percent, about 70to 98 weight percent, about 80 to 98 weight percent, or about 90 to 98weight percent.
 10. The composition of claim 3, wherein the aliphaticpolyester comprises polybutylene succinate or polybutylene succinateadipate.
 11. The composition of claim 2, wherein the thermoplasticpolyester comprises an aromatic polyester.
 12. The composition of claim11, wherein the aromatic polyester comprises a polyethyleneterephthalate.
 13. The composition of claim 12, wherein the polyethyleneterephthalate comprises a co-monomer.
 14. An article comprising thecomposition of claim
 1. 15. The article of claim 14, wherein the articleis in the form of a fiber, filament, rod, tube, or film.
 16. A process,comprising:
 1. an article from the composition of claim
 1. 17. Anarticle made by the process of claim
 16. 18. A composition comprising:at least one type of thermoplastic polyester; and a nucleant comprisinga compound of the formula:

wherein: R₁ is a hydrogen atom or an alkyl group having 1 to 4 carbonatoms; R₂ and R₃ are each a hydrogen atom or an alkyl group having 1 to12 carbon atoms; M is a group III or IV metal atom; X is HO, O═, or(HO)₂; and the composition is substantially devoid of alkali-metalcarboxylates, alkali metal β-diketonates, alkali metal salts ofβ-ketoacetic esters, and polyethylene terephthalates.
 19. A process,comprising: forming an article from the composition of claim
 18. 20. Anarticle made by the process of claim
 19. 21. A method of fabricating athermoplastic composition, comprising: contacting a thermoplasticpolyester with a nucleant having a chemical formula selected from thegroup consisting of:

and combinations of any two or more thereof; wherein: each R¹ isindependently H, NR²R², OR², OH, SR², SOR², SO₂R², CN, COR², CO₂R²,CONR²R², NO₂, F, Cl, Br, or I; and each R² is independently H or C₁-C₆alkyl.
 22. A method of fabricating a thermoplastic compositioncomprising: contacting a thermoplastic polyester having a meltingtemperature below about 260° C. with methylbenzylidene sorbitol ordimethylbenzylidene sorbitol dissolved in a solvent; melting thethermoplastic polyester at a temperature below about 260° C.; andcooling the thermoplastic polyester, to thereby fabricate thethermoplastic composition.